JP2013240138A - Electrically driven actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small electrically-driven actuator.SOLUTION: An electrically-driven actuator includes: an electrically driven motor 10 having a rotor 10b and a stator 10a; and a rotation-linear motion conversion mechanism 20 having a linear motion shaft 20a and a nut 20b and converting rotation motion into linear motion. The electrically driven motor 10 and the nut 20b of the rotation-linear motion conversion mechanism 20 are serially arranged relative to a linear motion direction of the rotation-linear motion conversion mechanism 20. The rotor 10b of the electrically driven motor 10 is attached to a sleeve 20c rotating with the nut 20b, and the sleeve 20c has a space 20d in which the linear motion shaft 20a is inserted.

Description

  The present invention relates to an electric actuator that is linearly driven, and more particularly, to an electric actuator that includes an electric motor and a rotation / linear motion conversion mechanism that is a mechanism element that converts the rotational motion of the electric motor into linear motion.

  In general, as a drive mechanism that generates a high thrust in the vertical direction, a hydraulic cylinder, an electric actuator that is linearly driven, and the like are known. The structure of the electric actuator that drives linearly combines an electric motor that rotates as a drive source and a ball screw mechanism that is one of the rotary / linear motion converting mechanisms that convert the rotational motion of the electric motor into linear motion. This can be achieved.

  For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-073320), a direct drive system in which an electric motor is configured on the outer periphery of a nut of the ball screw mechanism is used to provide a ball screw mechanism fixed to the rotor of the electric motor. A configuration is disclosed in which a nut is rotated and a screw shaft (linear motion shaft) that is screwed with the nut is linearly driven.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2007-187262), a nut member of a ball screw mechanism is rotatably supported by a housing in a state where the nut member is inserted into a rotor magnet (rotor) of an electric motor. This is a direct drive system that rotates integrally with the rotor magnet (rotor), and the output shaft (linear motion shaft) is inserted into the nut member, and a ball is interposed between the ball groove on the outer peripheral surface and output. A structure of an electric actuator is disclosed in which a shaft (linear motion shaft) is linearly driven in the axial direction by rotation of a nut member accompanying rotation of a rotor magnet (rotor).

JP 2005-073320 A JP 2007-187262 A

By the way, in an electric actuator for linear motion drive comprising an electric motor and a rotary / linear motion conversion mechanism that converts the rotational motion of the electric motor into linear motion, if the movement amount of the linear motion shaft is long, the total length of the electric actuator is The entire electric actuator becomes larger because of its elongation.
Further, in the direct drive system in which the electric motor is configured on the outer periphery of the nut of the rotation / linear motion conversion mechanism as in Patent Document 1 and Patent Document 2, the overall length can be suppressed, but the outer diameter of the electric motor is increased. The whole becomes larger.

  Therefore, for example, in high-thrust drive mechanisms that currently use hydraulic cylinders, electric actuators can be used instead of hydraulic cylinders for the purpose of improving the maintainability by eliminating the need for energy saving and oil by electrification. In the case of studying, it is difficult to mount the electric actuator because the electric actuator has a problem that it is large in size and long in order to be mounted on an existing device having a drive mechanism using a hydraulic cylinder.

  Therefore, an object of the present invention is to provide a small electric actuator.

  In order to solve such a problem, the present invention includes an electric motor having a rotor and a stator, a linear motion shaft and a nut, and a rotation / linear motion conversion mechanism that converts rotational motion into linear motion, The electric motor and the nut of the rotary / linear motion converting mechanism are arranged in series with respect to the linear motion direction of the rotary / linear motion converting mechanism, and the rotor of the electric motor is attached to a sleeve that rotates together with the nut. The electric actuator is characterized in that the sleeve has a space through which the linear motion shaft is inserted.

  According to the present invention, an electric actuator that is smaller than the conventional one can be provided.

It is a longitudinal cross-sectional view of the electric actuator which concerns on 1st Embodiment. It is a longitudinal cross-sectional view of the electric actuator which concerns on 1st Embodiment in the state which the linear motion shaft moved to the maximum moving amount. It is a schematic block diagram of the electric actuator which concerns on 1st Embodiment. It is a schematic block diagram of the electric actuator which concerns on 2nd Embodiment. It is a schematic block diagram of the electric actuator which concerns on a 1st comparative example. It is a schematic block diagram of the electric actuator of the direct drive system which concerns on a 2nd comparative example. It is a schematic block diagram of the electric actuator of the direct drive system which concerns on a 3rd comparative example.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

<< First Embodiment >>
An electric actuator 100A according to the first embodiment will be described with reference to FIG. FIG. 1 is a longitudinal sectional view of an electric actuator 100A according to the first embodiment.

  As shown in FIG. 1, an electric actuator 100A that is linearly driven includes an electric motor 10 that is rotationally driven as a drive source, a rotary / linear motion conversion mechanism 20 that converts the rotational motion of the electric motor 10 into a linear motion, and an encoder 30. And a thrust bearing 40, a slider 50 composed of a slider mover 50a and a slider stator 50b, a pressing plate 60, and a cylindrical housing 70.

  The rotation / linear motion conversion mechanism 20 includes a linear motion shaft 20a having a spiral groove and a nut 20b having a spiral groove, and the nut 20b is screwed to the linear motion shaft 20a. .

  A pressing plate 60 is fixed to the tip of the linear motion shaft 20a, and a slider movable element 50a is disposed on the pressing plate 60. The slider mover 50a is configured to be movable only in the linear motion direction along a slider stator 50b coupled to a structure (not shown) on which the electric actuator 100A is mounted. That is, the slider 50 (the slider movable element 50a and the slider stator 50b) prevents the rotational movement of the linear motion shaft 20a, and can move the linear motion shaft 20a only in the linear motion direction.

  Therefore, the rotation / linear motion converting mechanism 20 can linearly move the linear motion shaft 20a in the spiral direction of the linear motion shaft 20a by rotating the nut 20b.

  The electric motor 10 has a stator 10a fixed to the housing 70 and a rotor 10b, and functions as a drive source for rotating the nut 20b of the rotation / linear motion converting mechanism 20, The linear motion conversion mechanism 20 is arranged in series with the linear motion conversion mechanism 20 with respect to the linear motion direction of the linear motion shaft 20a.

The rotor 10b of the electric motor 10 is configured to be attached to the nut 20b of the rotation / linear motion conversion mechanism 20 arranged in series.
Specifically, a sleeve 20c extending from the nut 20b in the linear motion direction is formed, and the rotor 10b is attached to the outer peripheral surface of the sleeve 20c.
Further, a space 20d is formed inside the sleeve 20c, and the linear motion shaft 20a is accommodated when the electric actuator 100A is contracted.

  The outer diameter of the sleeve 20c is configured to be smaller than the outer diameter of the nut 20b. Further, the inner diameter of the sleeve 20c (space 20d) is configured to be larger than the outer diameter of the linear motion shaft 20a. When the linear motion shaft 20a is stored, the sleeve 20c and the linear motion shaft 20a are not in contact with each other. It is comprised so that.

  The rotating member composed of the nut 20b and the sleeve 20c is fixed to the housing 70 on the outer peripheral surface of the nut 20b via a thrust bearing 40 that mainly receives a thrust load in one direction. On the opposite side of the bearing 40, it is fixed to the housing 70 via the bearing 10c.

  The encoder 30 can detect the position and / or movement speed of the pressing plate 60 by detecting the rotation angle and / or rotation speed of the rotating member (nut 20b, sleeve 20c).

  Therefore, by driving the electric motor 10, the rotor 10b and the rotary members (nuts 20b, sleeves 20c) attached thereto can be rotated.

  With the configuration described above, the electric actuator 100A drives the electric motor 10 to rotate the rotor 10b and the rotating members (nuts 20b, sleeves 20c) attached thereto, thereby moving the linear motion shaft 20a to the linear motion shaft. It can be moved linearly in the spiral direction of 20a.

  FIG. 2 is a longitudinal sectional view of the electric actuator 100A according to the first embodiment in a state where the linear motion shaft 20a has moved to the maximum movement amount.

  As shown in FIG. 2, the linear motion shaft 20 a moves in the direction opposite to the electric motor 10, so that a space 20 d generated by the movement of the linear motion shaft 20 a is formed inside the rotor 10 b of the electric motor 10. The Thus, the inside of the rotor 10b of the electric motor 10 can be used as a moving space for the linear motion shaft 20a.

<Contrast with comparative example>
Here, the structure of the electric actuator 100A according to the first embodiment is compared with the electric actuator 100C according to the first comparative example shown in FIG. 5 and the electric actuator 100D according to the second comparative example shown in FIG. This will be described with reference to FIG.
In the description of FIGS. 3, 5, and 6 (and FIGS. 4 and 7 described later), the encoder 30, the slider 50, the housing 70, and the like are omitted as appropriate in order to show the main components in an easily understandable manner. It is shown.

  First, the general structure of a general electric actuator will be described with reference to FIG. In particular, the configuration of an electric actuator when applied to a drive mechanism that can output high thrust and that receives an excessive thrust load mainly in one direction is shown. FIG. 5 is a schematic configuration diagram of an electric actuator 100C according to the first comparative example.

The electric actuator 100C includes, as main components, an electric motor 10, a linear motion shaft 20a and a nut 20b of the rotation / linear motion conversion mechanism 20, a thrust bearing 40 that receives a thrust load, and a pressing plate 60. .
The rotor 10b of the electric motor 10 is fixed to the nut 20b of the linear motion conversion mechanism 20 via the connecting member 20e, and the nut 20b rotates by the rotational movement of the electric motor 10. The linear movement shaft 20a screwed into the nut 20b is linearly moved by the rotational movement of the nut 20b, and the thrust bearing 40 that receives the thrust load is disposed on the outer periphery of the nut 20b.

Here, the length of the electric actuator 100C in the linear motion direction will be examined.
The linear movement shaft 20a needs to be equal to or greater than the maximum movement amount L1 of the linear movement shaft 20a and the length Hn1 of the nut 20b, and the linear movement shaft 20a corresponding to the maximum movement amount L1 is between the electric motor 10 and the rotary / linear motion conversion mechanism 20. It is necessary to secure a moving space.
Therefore, the length of the electric actuator 100C in the linear motion direction needs to be “Hm + L1 + Hn1”, which is the sum of the length Hm of the electric motor 10, the maximum movement amount L1 of the linear motion shaft 20a, and the length Hn1 of the nut 20b.
Thus, the electric actuator 100C according to the first comparative example is vertically long in the linear motion direction, and is further vertically long depending on the maximum movement amount L1.

  Therefore, in order to shorten the length of the electric actuator in the linear motion direction, a direct drive type electric actuator as shown in FIG. 6 that directly drives the nut 20b is known. FIG. 6 is a schematic configuration diagram of a direct drive type electric actuator 100D according to a second comparative example.

The electric actuator 100D is configured such that the electric motor 10 is configured on the outer periphery of the nut 20b, and the nut 20b is directly driven by the electric motor 10.
Therefore, the length of the electric actuator 100D in the linear motion direction needs to be “L1 + Hn1” that is the sum of the maximum movement amount L1 of the linear motion shaft 20a and the length Hn1 of the nut 20b, and the electric actuator 100C according to the first comparative example. Compared to (see FIG. 5), the length can be shortened by the length Hm6 of the electric motor 10.

However, the outer diameter φDm6 of the electric motor 10 is increased by arranging the electric motor 10 on the outer periphery of the nut 20b.
Further, the nut 20b of the rotation / linear motion conversion mechanism 20 has a structure that is easily affected by heat generated by the electric motor 10 arranged on the outer periphery, and when the ball / screw mechanism, which is a precise mechanism element, is used for the rotation / linear motion conversion mechanism 20. Measures that take into account the effects of heat are required.

  The configuration of the electric actuator 100A according to the first embodiment will be described with reference to FIG. FIG. 3 is a schematic configuration diagram of the electric actuator 100A according to the first embodiment.

  In order to reduce the outer diameter φDm6 of the electric motor 10 shown in FIG. 6, in the electric actuator 100A, the electric motor 10 and the nut 20b are arranged in series with respect to the linear motion direction. Further, the rotor 10b and the nut 20b of the electric motor 10 are fixed in series, and a space 20d (see FIGS. 1 and 2) is provided for the linear motion shaft 20a to pass through the center of the rotor 10b.

  Further, since the outer diameter of the electric motor 10 is set to φDm1, which is approximately the same as the outer diameter φDb1 of the thrust bearing 40, and the output torque of the electric motor 10 is made equal to the electric motor 10 of the electric actuator 100D (see FIG. 6), the electric actuator 100A The length Hm1 of the electric motor 10 is expanded from the length Hm6 (see FIG. 6) of the electric motor 10 in the electric actuator 100D (see FIG. 6).

Here, if “the length Hm1 of the electric motor 10 ≦ the maximum movement amount L1 of the linear movement shaft 20a”, the linear movement direction length of the electric actuator 100A is the maximum movement amount L1 of the linear movement shaft 20a and the nut 20b. It becomes “L1 + Hn1”, which is the sum of the lengths Hn1, and can be shortened similarly to the electric actuator 100D (see FIG. 6).
In addition, the maximum outer diameter of the electric actuator 100A is φDm1 (φDb1), which can be made smaller than the maximum outer diameter φDm6 of the electric actuator 100D (see FIG. 6).

  Further, as shown in FIGS. 1 and 2, the electric actuator 100A has a structure in which the housing 70 approaches a cylindrical shape, has less unevenness, and uses space effectively. The configuration is easy to apply to the driving device of the used device. Of course, when considering replacement with a hydraulic cylinder, a compressor is unnecessary, and maintenance is improved because no oil is required.

  Further, as shown in FIGS. 1 to 3, the electric actuator 100 </ b> A has the electric motor 10 and the nut 20 b arranged in series, so that the electric motor 10 generates more heat than the electric actuator 100 </ b> D shown in FIG. 6. It is hard to receive. In addition, since the nut 20b is not disposed inside the electric motor 10, the structure can be easily cooled by a fan or the like from the outer periphery of the nut 20b.

<< Second Embodiment >>
The electric actuator 100A (see FIG. 3) according to the first embodiment has been described as “the length Hm1 of the electric motor 10 ≦ the maximum movement amount L1 of the linear motion shaft 20a”.
In the electric actuator 100B according to the second embodiment (see FIG. 4), the maximum movement amount of the linear movement shaft 20a is short, that is, “the maximum movement amount L2 of the linear movement shaft 20a of the electric actuator 100B (see FIG. 4) < The maximum movement amount L1 of the linear movement shaft 20a of the electric actuator 100A (see FIG. 3) ”,“ the maximum movement amount L2 of the linear movement shaft 20a of the electric actuator 100B (see FIG. 4) <the length Hm1 of the electric motor 10 ( The case of “See FIG. 3” will be described.
When “L2 (L1) <Hm1”, the length of the electric actuator 100A according to the first embodiment (see FIG. 3) is “Hm1 + Hn1”, and the electric actuator 100D according to the second comparative example (FIG. 6) is longer than the length “L1 + Hn1”.

The configuration of the electric actuator 100B according to the second embodiment will be described with reference to FIG. 4 while comparing with the electric actuator 100E according to the third comparative example shown in FIG. FIG. 4 is a schematic configuration diagram of an electric actuator 100B according to the second embodiment.
FIG. 7 is a schematic configuration diagram of a direct drive type electric actuator 100E according to a third comparative example. In the electric actuator 100D according to the second comparative example (see FIG. 6) and the electric actuator 100E according to the third comparative example (see FIG. 7), the maximum movement amount of the linear motion shaft 20a is L1 and L2 (L2 <L1). ), Except for the differences, the description is omitted.

In the electric actuator 100B, the length Hm2 of the electric motor 10 is designed to be short so that “the length Hm2 of the electric motor 10 ≦ the maximum movement amount L2 of the linear motion shaft 20a”.
Moreover, in the electric actuator 100B, in order to make the output torque of the electric motor 10 equal to that of the electric motor 10 of the electric actuator 100E (see FIG. 7), the electric motor 10 is designed by making the stator 10a and the rotor 10b thick. The outer diameter of 10 is expanded to φDm2. Here, in the electric actuator 100B, the outer diameter φDm2 of the electric motor 10 and the outer diameter φDb2 of the thrust bearing 40 are designed to satisfy φDm2≈φDb2, and the outer diameter of the nut 20b is set to φDn2 in accordance with the inner diameter of the thrust bearing 40. By designing the length of the nut 20b to Hn2, the length of the electric actuator 100B in the linear motion direction becomes “L2 + Hn2”, which is shorter than the length of the electric actuator 100E (see FIG. 7) in the linear motion direction “L2 + Hn1”. be able to. In addition, the electric actuator 100B has a structure that approaches a cylindrical shape, has less unevenness, and effectively uses space.

  The above configuration can be realized by using the rotation / linear motion conversion mechanism 20 that can change the outer diameter shape from the elongated structure to the thick / short structure without changing the thrust limit load value received by the rotation / linear motion conversion mechanism 20. is there.

  For example, when a ball screw mechanism is applied as the rotation / linear motion conversion mechanism 20, the ball screw mechanism includes a linear motion shaft 20a having a spiral ball screw groove and a nut 20b having a spiral ball screw groove. In this structure, a plurality of balls are brought into point contact with the ball screw groove of the nut 20b to support a thrust load.

  For this reason, the maximum thrust load of the ball screw mechanism is obtained from the number of balls contacting the ball screw groove portion of the linear motion shaft 20a and the limit load per ball due to the size of the balls. As a result, the shape of the nut 20b changes.

  Roughly speaking, to make the nut shape of a thick and short structure with a constant thrust limit load value, the outer diameter of the ball is enlarged to increase the load resistance of one ball, and the number of balls arranged in a spiral shape is reduced. This can be achieved.

  The same applies to the case where a trapezoidal screw mechanism is applied as the rotation / linear motion converting mechanism 20. That is, if the contact area with the nut 20b is expanded by enlarging the trapezoidal groove, the length of the nut 20b in the linear motion direction can be designed to be short.

  Even in the rotation / linear motion conversion mechanism 20 other than the ball screw mechanism and the trapezoidal screw mechanism described above, the same effect can be obtained by using the rotation / linear motion conversion mechanism 20 having a variable nut shape at the same thrust limit load.

  With the configuration described above, it is possible to reduce the size of the electric actuator, and it is possible to provide an electric actuator having a configuration approximate to a cylindrical shape with less unevenness. For this reason, it can be easily applied to a drive mechanism using a hydraulic cylinder at present, and it can be expected that the compressor is indispensable for the hydraulic cylinder, and that the maintenance is improved by eliminating the need for oil.

<Modification>
The electric actuators 100A and 100B according to the present embodiment (the first embodiment and the second embodiment) are not limited to the configuration of the above-described embodiment, and various modifications can be made without departing from the spirit of the invention. Is possible.

  The electric actuators 100A and 100B according to the present embodiment have been described for the electric actuator that requires a thrust bearing 40 that requires a high thrust and supports an excessive thrust load in one direction. However, the radial load, the thrust load, and The same applies to a structure that receives both a radial load and a thrust load, and is not limited to the above.

  Further, the thrust bearing 40 has been described as a structure that receives a high load by using a plurality of angular ball bearings that are suitable for receiving a unidirectional thrust load or a rigid load, but the same applies to a structure that uses a thrust ball bearing. It is possible to reduce the size regardless of the type.

DESCRIPTION OF SYMBOLS 10 Electric motor 10a Stator 10b Rotor 10c Bearing 20 Rotation linear motion conversion mechanism 20a Linear motion shaft 20b Nut (rotating member)
20c Sleeve (Rotating member)
20d Space 30 Encoder 40 Thrust bearing 50 Slider 50a Slider mover 50b Slider stator 60 Press plate 70 Housing 100A, 100B Electric actuator

Claims (6)

An electric motor having a rotor and a stator;
A rotation / linear motion conversion mechanism that has a linear motion shaft and a nut and converts rotational motion into linear motion;
The electric motor and the rotation / linear motion conversion mechanism nut are arranged in series with respect to the linear motion direction of the rotation / linear motion conversion mechanism,
The rotor of the electric motor is attached to a sleeve that rotates together with the nut,
The electric actuator characterized in that the sleeve has a space through which the linear motion shaft is inserted. The stator outer diameter of the electric motor is
2. The electric actuator according to claim 1, wherein the electric actuator is approximately equal to a bearing outer diameter of a bearing pivotally attached to an outer periphery of the nut of the rotation / linear motion conversion mechanism. The maximum movement amount of the linear motion shaft of the rotary / linear motion conversion mechanism is:
The electric actuator according to claim 1, wherein the electric actuator is configured to be equal to or greater than an axial width of the electric motor. The stator outer diameter of the electric motor is configured so that the axial direction width of the electric motor and the maximum movement amount of the linear motion shaft of the rotary / linear motion conversion mechanism are approximately the same,
The bearing outer diameter is configured so that the outer diameter of the stator of the electric motor is approximately the same as the bearing outer diameter of a bearing that is attached to the outer periphery of the nut of the rotary / linear motion conversion mechanism. The electric actuator as described. The rotation / linear motion conversion mechanism is:
The electric actuator according to claim 1, wherein a helical groove formed on the linear motion shaft and the nut are screwed together. The space is
The electric actuator according to claim 1, wherein the electric actuator is configured with an outer diameter of a linear motion shaft of the rotation / linear motion conversion mechanism.

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